Dynamo-electric machine.



C. J. FBGHHEIMER. DYNAMO ELEGTRIU MACHINE.

AHLIUATION FILED MAY 13, 1909. 982,806. Patented .13.11.31, 1911.

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DYNAMO ELECTRIC MACHINE.

APPLICATION FILED MAY 13, 1909. 982,806. Panam-,ed Jan.31i1911 2SHEETS-'SHEET 2.

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UNITED sTATEs PATENT oEEIoE.

CARL J. FECHHEIMER, OF MILWAUKEE, WISCONSN, .ALSSIGNOR TO ALLIS-CHALMERSCOMPANY, A CORPORATION 0F NEW JERSEY.

DYNAMO-ELECTRIC MACHINE.

Specification of Letters Patent.

Application filed May 13, 1909, Serial No. 495,761.

T o all whom it may concern:

lle ity known that l, CARI. J. FECHHEIMER, a citizen of the UnitedStates, residing at- Milwaukee` in the county of Milwaukee and State ol''isconsin, have invented certain new and useful Improvements in Dynamo-.l'llcctric Machines, of which the following is a l'ull, clear, andexact specification.

This invention relates to dynamo-electric machines and particularly tohigh speed machines such as turbo-alternators having rotating fieldmagnets.

ln dynamo-electric machines and particularly in high speed machineshaving rotatiug elements provided at the ends with rings or equivalentmeans for retaining inv position the end portions of the coils, there isa leakage of the field flux at. theends of the machine and particularlythrough the coil retaining means. This magneticleakage is undesirablefor several reasons among which is` it necessitates more field ampere-`turns and consequently a greater weight of copper and a larger corecross section for a certain voltage, load and power factor, than wouldbe required if all the tiux passed across the air gap between the coresof the rotating and stationary elements. Furthermore this magneticleakage is undesirable particularly in machines of certain types anddesigns, for the reason that it causes an unequal distribut-ion of fluxaxially the tiux density being greater at the middle of the machine thanat the ends. This unequal f distribution of flux is more marked in somemachines than others, being greater in those machines having rotatingfield magnets provided at intervals with air gaps, for the reason thatthe air gaps increase the reluctances of the .magnetic paths axiallythrough the rotor core, and therefore prevent an equalization of thellux density. This unequal distribution of tiux causes the core lossesand the *heating incident thereto to be greater at the middle of themachine than at the ends.

The object of the invention is to so construct dynamo-electric machinesthat this magnetic leakage will be greatly decreased, and a practicallyuniform flux density-obtained.

In carrying out my invention I so construct the machine and preferablythe rotor or rotary element thereof that when the machine is inoperation, the end portions ofv the rotor core are highly saturated andare worked at a. higher tiux density than the intern'iediate portions.At the same time I cause the `gap or clearance between the end portionsof the rotor core and the corresponding portions of the stator core tobe less than the clearance atl the middle of the machine, so that thereluctance of the air gap will be less at the ends of the machine thanintermediate the ends, and I also increase the reluctances of themagnetic paths from pole to pole through the retaining means for the endor projecting portions of the coils carried by the rotor. In thepreferred form of my invention the air gap or clearance is varied bymaking the diameter of the-rotor core greater at the ends than betweenthe ends, thereby causing the density of the flux passing between theend portions of the cores of the rotary and stationary members to begreater than it would be if the diameter of the core of the rotarymember were uniform. The diameter and cross sectional areas of the endportions of the rotor core, which portionsare preferably separated fromthe intermediate portions of the core by gaps or spaces of highreluctance, are such that the densityof the flux passing between thecores of the rotary and stationary elements is practically uniform fromone end of the machine to the other, and at the same time these endportions of` the rotary core are highly saturated. This construction,together with the fact that the reluctances of the magnetic paths frompole to pole through the coil retaining means at the end of the core aremade very high, reduces the magnetic leakage to a minimum.

. My invention may be further briefly summarized as consisting incertain novel details of construction and combinations of parts whichwill be described in the speciication and set forth in the appendedclaims.

Reference is had to the accompanying sheets of drawings in Which- Figure1 is a vertical sectional elevation of a turbo-alternator constructed inaccord'- ance with my invention, the alternator having a cylindricalrotary field core which in. this case is built up of a number of rigiddisks and having field coils which project beyond the core and aresurrounded by coil Patented Jan. 31, 1911.

retaining rings. Fig. 2 is a transverse secmember, the section beingtaken substantially along the line 2-2 of Fig. 1 looking in thedirection indicated by the arrows. Fig. 3 is a view half in section andhalf in elevation, of a rotary field member of a high speed alternatorconstructed in accordance with my invention and having its core built upof sheet metal punchings or laminae.

Referring now to the figures of the drawings, 10 represents a housing orcasing which incloses the machine and which is provided to deaden thenoise incident to iigh speeds of rotation and to permit properventilation. This housing includes a central ribbed portion whichsupports an annular laminated stator or armature core 11 which isprovided with the usual armature Winding 12. Extending through the endsof the housing is a shaft 13 on which the rotor or rotary field magnetis secured. This rotor is provided with a cylindrical core 14, theconstruction of which may be varied to a considerable degree and willdepend upon the size and the speed to which the rotor is to besubjected. As shown in Fig. 1 the core is built up of a definite numberof rigid circular forged steel disks the two outer or end disks beingdesi nated 14'L and the disks between the end disks being designated14". The disks are mounted on thc shaft in direct engagement with oneanother for a purpose to be explained later, and are held in position byclamping nuts l5. The core is provided, as shown in Fig. 2, with radialslots forming teeth 16 and poles 17 (a four-pole machine being shown inthis instance) and these slots receive the sides of field coils 1S whichare preferably formed of edgewise wound strap copper, the coils beingarranged concentrically about each pole and being retained in the slotsby wedges 19 which preferably extend entirely across the core. The coilsare provided with end portions 20 which project beyond the core and areheld in position against displacement by centrifugal force by coilretaining means which consistin this case of rigid rings 21 formed ofsome material such as steel possessing high tensile strength, theserings engaging at their inner ends and being partially supported by thetwo end or outer disks 14a and at their outer ends engaging rings 22which may be formed of bronze and are supported by the shaft.

As is shown clearly in Fig. 1 the end disks 14L are greater in diameterthan the intermediate disks 14", the latter in this case being all ofuniform diameter. Furthermore the effective cross sectional areas orwidths of at least the outer portions of the 'end disks 14El are madeless than the cross sec` tional areas or widths of the disks 14" andthis I accomplish in this case by thinning or removing portions of theinner sides of the end disks so as to form circumferential air gaps 23of considerable reluctance, which air gaps separate the outer portionsof the end disks from the corresponding portions of the adjacent disks14b and prevent to a larve extent the passage of flux between disks14and the adjacent disks 14". lf desired, to decrease still further thecross scrtional areas of the end disks, axial openings 24 may beprovided in the pole portions of said disks. These openings also permita circulation of air Iaround the end portions of the coils. The diameterof the end disks is preferabl suchthat when the machine `is in operat1onthe density of the flux pass- .is therefore choked back, so to speak. As

was stated before and as shown in the drawings the intermediate disks14'J are in direct engagement with one another, and therefore theremaybe an equalization of the flux densities in these disks. The air gaps23, however, prevent to a large extent the passage of flux between theouter ortions of the disks 14 and the correspon ing portions of the enddisks 14". To decrease still fur* ther the leakage of fluxthrough therings, I make the area of the bearing surfaces ot'l the rings upon theend disks as small as possible, consistent with strength and rigidity ofconstruction, and for this purpose the outer portions of the end disks14 are provided with annular recesses or notches 25 forming annularshoulders. The inner portions of the rings are also provided withannular recesses, and these last named recesses receive the outerportions only of the shoulders formed by the recesses in the end disks,

the inner edges or faces ofthe rings being separated by narrow slots orair gaps 2G from the vertical faces of the annular recesses 25.Furthermore the portions of the end rings opposite the poles are cutaway or notched as shown at 27 so as to increase still further thereluctances of the magnetic paths from pole to pole through the rings.

In Fig. 3 I have shown a rotor having its core 28 built up of laminae,but which like the rotor first described, is constructed so that asubstantially uniform flux density will be obtained from one end of themachine to the other and so that magnetic leakage through the end ringswill be greatly diminished. The core is provided with slots whichreceive the side portions of the field coils, the latter having portions29 which project beyond the ends lll5 of the core and are inclosed andretained in position by end rings 30. -In this instance the vi'otor hasat the ends of the core, plates or disks 3l which are preferably formedof lion-magnetic matei'ial, and the rings 30, instead of engagingdirectly the ends of the core, engage the peripheries of these plates ordisks 31. As in the construction first described, the outer ends of therings 30 engage rings 32 which are supported by the-shaft. These disks31, which are engaged by the inner ends of the rings 30, diminish tosome extent the leakage which.

Vhaving rotors which are so designed and constructed that disks ofnon-magnetic ma- .terial cannot be conveniently or safely secured to theends of the rotor cores. It will be seen that the core 28 is provided atits ends with sections 33 which are of greater di.- aineter than themain or intermediate portion 34 and are separated from vsaidintermediate portion by circumferential air gaps or spaces 35, these airgaps being formed by separating or spacing part of the' laminae at theends of the core from the main body of the latter. The intermediateportion 84, as is shown in the drawing, is not provided with air gaps orcircumferential Ventilating spaces usually provided in machines of thistype and inasmuch as all the laminae of this portion of the core are indirect engagement with one another there may bean equalization of theflux density between different paits of this portion of the core. Thegaps 35 however vprevent to a large extent the passage of flux betweenthe end sections or portions and the intermediate portion 34. rIhediameter and the axial Widths of the end sections are made such thatwhen the machine is in operation the density of theI flux passingbetween the coresv of the rotary and stationary members will besubstantially uniform from one end of the machine to the other or willbe the same at the ends of the machine as at any point between the endsand at the saine time these end sections will be highly saturated. As inthe construction first described, the rings 30 are provided opposite thepoles of the core with notches or recessed portions 36 which in# creasethe reluctaiices of the magnetic paths from pole to pole through therings. Therefore in the rotor shown in Fig. 3, the magnetic leakagethrough the end rings will be very small.

I do not desire to be confined to the'eX- act details shown but aim inmy claims to cover all modifications which do not involve a departurefrom the spirit and scope of my invention.

3. In a dynamo-electric machine, a rotary member having acore, the endportionsl of which are of greater diameter than the intermediateportion, are contiguous with the latter near the center, and areseparated therefrom near the periphery by gaps .or spaces of highreluctance.

4. In a dynamo-electric machine, a rotary member having a core providedat the ends with portions which are of greater 'diameter than theintermediate portion of the core, are separated therefrom near theperiphery by spaces. or gapsv of high reluctance, and are thicker nearthe center thannear the periphery.

5. In a dynamo-electric machine, rotary and stationary members havingcores which are separated by an air gap or clearance space, theclearancebetween the ends of the cores being less than the clearancebetween the middle portions of the cores, and the rotary core having endportions which are thicker near the center than near the periphery.

6. In a dynamo-electric machine, rotary and stationary members havingcores which are separated by an air gap or clearance space, the ends ofthe rotary core being greater in diameter than the intermediate portionthereof sothat the reluctance ot' the air gap is less at the ends of'the machine than intermediate the ends, and said end portions of therotary core being thinner near the periphery than near the center.

7. In a dynamo-electric machine, rotary and stationary members havingcores which are separated by an air gap or clearance space, the ends ofthe rotary core being greater in diameter than the intermediate portionthereof so that the reluctance of the air gap is less at the ends of themachine than intermediate the ends. .and said end portions of the rotarycore being separated at the periphery from the intermediate poi'- tionthereof by air gaps.

8. A rotor for adynamo-electric machine comprising a core and coilswhich project beyond the ends of the core, means formed of magneticmaterial for `retaining the projecting portions of the coilsv inposition, the portions of the core adjacent said coil-retaining meanslbeing of greater diameter than the intermediate portion of the core andbeing separated therefrom near the periphery by gaps of considerablereluctance.

t). In a rotor for a dynamo-electric.inaehine, a cylindrical core, coilscarried by said core andprojecting beyond the ends thereof, rings ofmagnetic material surrounding said projecting portions of the coils, theportions of the core adjacent the rings .being of greater diameter thanthe intermediate portion of the core and being separated thereirom atthe periphery by spaces of high rcliu-tance.

10. A rotor for a dynamo-electric machine comprising a cylindrical corehavin" coils which project beyond the ends thereof, rings ot' magneticmaterial surrounding the projecting portions of the coils, said core having near the ends thereof circumferential gaps` the portions of thecore beyond the gaps being of greater diameter than the portion betweenthe gaps.

11. In a rotor for a dynamo-electric machine, a cylindrical core havingcoils which project beyond the ends thereof, rings of magnetic materialsurrounding the projecting portions of the coils and engaging the endsof the core, said c'ore having near the ends circumferential air gaps,the portions of the core beyond the air gaps being of greater diameterthan the portion between the gaps and having cross sections such thatsaid portions are saturated when the core is magnetized.

1Q. A rotor for a dynamo-electric inachiue comprising a cylindrical coreformed of a definite number of rigid disks, field coils carried by saidcore and projecting axially beyond the ends thereof, end rings ot'magnetic material surrounding the projecting portions of the coils, saidend disks being of greater diameter than the intermediate disks andhaving portions separated therefrom by spaces or gaps of highreluctance.

13. In a dynamo-electric machine, a rotary field member comprising acylindrical core formed of a plurality of disks arranged side by side`field coils carried by the core and projecting axially beyond the endsthereof. rings` ot' magnetic material surrounding the projectingportions of the coils and engaging the two end disks, said end disksbeing of greater diameter than the intermediate disks and-the outerportions of said end disks being of less thickness than thecorresponding portions of the intermediate disks.

ll. In a dynamo-electric machine, a rotary field member comprising aplurality ot disks, the two outer or end disks being of greater diameterthan the intermediate disks` and the intermediate disks being ofuniformdiameter and being in engagement with one another, and said end diskshaving por-" tions removed from their inner sides forming annular airgaps between said end disks and the adjacent disks, and-field coilscarried by said core.

15. In a dynamo-electric machine, a rotary cylindrical field core havingcoils which project axially beyond the ends thereof, rings of magneticmaterial surrounding thc-projecting portions of the coils and engaging'the ends of the core, said rings having recesses or vnotches oppositethe poles of the core, portions of the core adjacent the rings being ofgreater dialneter than portions remote from the rings.

1G. In a dynamo-electric machine, a rotary cylindrical field corecomposed of a plurality of disks having slots, coils located in saidslots and projecting axially beyond the ends of the core, rings ofmagnetic material surrounding the projecting portions of thel coils andengaging the end disks, said rings having recesses or notches oppositethe field poles, and said end disks being of greater diameter than theremaining disks and being separated from the latter near the peripheryby annular spaces ot high reluctance.

17. In a dynamo-electric machine, a rotary cylindrical core consistingof rigid nteel disks arranged side by side with their adj acentfaces inengagement, the two outer or end disks being of greater diameter thanthe remaining disks and portions of the end disks and the disks adjacentthereto being separated near the periphery by annular air gaps, saidcore having groups of radial slots forming teeth and field poles, coilslocated in the slots and projcctingaxially beyond the ends of the core,rings of magnetic material surrounding the projecting portions of thccoils and engaging the end disks. said rings having recesses or notchesopposite the field poles.

18. In a dynamo-electric machine. a rotary cylindrical field core havingcoils which project axially beyond the ends thereof, and rings ofmagnetic material surroumling the projecting portions of the coils andengaging the ends of the core, said rings having recesses or notchesopposite the poles of the core.

19. In a dynamo-electric machine, rotary and stationary members havingcores which are `separated by an air gap or clearance space, the core ofthe rotary member having end portions which are separated at theperiphery from the middle portion by air gaps, the clearance spacebetween the end portions of the cores of the rotary and stationarymembers being less than that between the middle portions of said cores.

Q0. In a dynanio-electric machine, a r0- tary member having a core builtup of rigid disks, said disks being all in engagement with one anothernear their centers, and the end disks at their peripheries beingseparated from the adjacent disks byair spaces.

21. In a dynamo-electric machine, a rotary member having a core built upof a number of disks all in engagement with one another, the end disksbeing cut away at the periphery on the sides toward the tary memberhaving a core of the cylindrical type provided with two peripheralgrooves near its two ends respectively, the section of the core which isbetween the two grooves being of smaller diameter than the two sectionsoutside said grooves.

Milwaukee, Wis., May 3, 1909.

In testimony whereof I alix my signature, in the presence of twowitnesses.

CARL J. FECHI-IEIMER.

Witnesses:

R. B. VILLIAMSON, CHAS. L. BYRON.

